Regeneration of ionic liquid catalyst by hydrogenation using a metal or metal alloy catalyst

ABSTRACT

A process for regenerating a used acidic ionic liquid catalyst which has, been deactivated comprising the steps of contacting the used chloroaluminate ionic liquid catalyst and hydrogen with a metal hydrogenation catalyst in a reaction zone under hydrogenation conditions for a time sufficient to increase the activity of the ionic liquid catalyst is described. In one embodiment, hydrogenation is conducted in the presence of a hydrocarbon solvent.

FIELD OF THE INVENTION

The present invention relates to methods for the regeneration ofcatalysts and more specifically to the regeneration of ionic liquidcatalysts.

BACKGROUND OF THE INVENTION

Ionic liquids are liquids that are composed entirely of ions. Theso-called “low temperature” Ionic liquids are generally organic saltswith melting points under 100 degrees C., often even lower than roomtemperature. Ionic liquids may be suitable for example for use as acatalyst and as a solvent in alkylation and polymerization reactions aswell as in dimerization, oligomerization acetylation, metatheses, andcopolymerization reactions.

One class of ionic liquids is fused salt compositions, which are moltenat low temperature and are useful as catalysts, solvents andelectrolytes. Such compositions are mixtures of components which areliquid at temperatures below the individual melting points of thecomponents.

Ionic liquids can be defined as liquids whose make-up is entirelycomprised of ions as a combination of cations and anions. The mostcommon ionic liquids are those prepared from organic-based cations andinorganic or organic anions. The most common organic cations areammonium cations, but phosphonium and sulphonium cations are alsofrequently used. Ionic liquids of pyridinium and imidazolium are perhapsthe most commonly used cations. Anions include, but not limited to, BF₄⁻, PF₆ ⁻, haloaluminates such as Al₂Cl₇ ⁻ and Al₂Br₇ ⁻, [(CF₃SO₂)₂N)]⁻,alkyl sulphates (RSO₃ ⁻), carboxylates (RCO₂ ⁻) and many other. The mostcatalytically interesting ionic liquids are those derived from ammoniumhalides and Lewis acids (such as AlCl₃, TiCl₄, SnCl₄, FeCl₃ . . . etc).Chloroaluminate ionic liquids are perhaps the most commonly used ionicliquid catalyst systems.

Examples of such low temperature ionic liquids or molten fused salts arethe chloroaluminate salts. Alkyl imidazolium or pyridinium salts, forexample, can be mixed with aluminum trichloride (AlCl₃) to form thefused chloroaluminate salts. The use of the fused salts of1-alkylpyridinium chloride and aluminum trichloride as electrolytes isdiscussed in U.S. Pat. No. 4,122,245. Other patents which discuss theuse of fused salts from aluminum trichloride and alkylimidazoliumhalides as electrolytes are U.S. Pat. Nos. 4,463,071 and 4,463,072.

U.S. Pat. No. 5,104,840 to describes ionic liquids which comprise atleast one alkylaluminum dihalide and at least one quaternary ammoniumhalide and/or at least one quaternary ammonium phosphonium halide; andtheir uses as solvents in catalytic reactions.

U.S. Pat. No. 6,096,680 describes liquid clathrate compositions usefulas reusable aluminum catalysts in Friedel-Crafts reactions. In oneembodiment, the liquid clathrate composition is formed from constituentscomprising (i) at least one aluminum trihalide, (ii) at least one saltselected from alkali metal halide, alkaline earth metal halide, alkalimetal pseudohalide, quaternary ammonium salt, quaternary phosphoniumsalt, or ternary sulfonium salt, or a mixture of any two or more of theforegoing, and (iii) at least one aromatic hydrocarbon compound.

Aluminum-containing catalysts are among the most common Lewis acidcatalysts employed in Friedel-Craft reactions. Friedel-Craft reactionsare reactions which fall within the broader category of electrophylicsubstitution reactions including alkylations.

Other examples of ionic liquids and their methods of preparation mayalso be found in U.S. Pat. Nos. 5,731,101; 6,797,853 and in U.S. PatentApplication Publications 2004/0077914 and 2004/0133056.

Hydrogenation in chloroaluminate ionic liquids in the presence of anelectropositive metal and HCl was reported by K. R. Seddon et al inChem. Commun., 1999, 1043-1044.

As a result of use, ionic liquid catalysts become deactivated, i.e. loseactivity, and may eventually need to be replaced. However, ionic liquidcatalysts are expensive and replacement adds significantly to operatingexpenses by in some cases requiring shut down of an industrial process.One of the heretofore unsolved problems impeding the commercial use ofchloroaluminate ionic liquid catalysts has been the inability toregenerate and recycle them. The present invention provides methods toregenerate acidic chloroaluminate ionic liquid catalysts overcoming thisobstacle and paving the way for the practical, commercial use of theseenvironmentally friendly catalysts.

SUMMARY OF THE INVENTION

Among other things, the present invention provides a process forregenerating a used acidic chloroaluminate ionic liquid catalystcomprising contacting the used chloroaluminate ionic liquid catalyst andhydrogen with a metal hydrogenation catalyst in a reaction zone underhydrogenation conditions for a time sufficient to increase the activityof the ionic liquid catalyst.

BRIEF DESCRIPTION OF THE FIGURE

The FIGURE is a block diagram of an embodiment of an ionic liquidcatalyst regeneration according to the invention.

DETAILED DESCRIPTION

The present invention relates to a process for the regeneration of spentor deactivated acidic ionic liquid-based catalysts i.e. those catalystswhich have lost all or some of their catalytic activity. The presentprocess is being described and exemplified with reference certainspecific ionic liquid catalysts and processes catalyzed thereby, butsuch description is not intended to limit the scope of the invention.The methods described may be applied to other catalysts and processes bythose persons having ordinary skill based on the teachings, descriptionsand examples included herein.

The specific examples used herein refer to alkylation processes usingionic liquid systems, which are amine-based cationic species mixed withaluminum chloride. In such systems, to obtain the appropriate aciditysuitable for the alkylation chemistry, the ionic liquid catalyst isgenerally prepared to full acidity strength by mixing one molar part ofthe appropriate ammonium chloride with two molar parts of aluminumchloride. The catalyst exemplified for the alkylation process isa1-alkyl-pyridinium chloroaluminate, such as 1-butyl-pyridiniumheptachloroaluminate.

In general, a strongly acidic ionic liquid is necessary for isoparaffinalkylation, e.g. isoparaffin alkylation. In that case, aluminumchloride, which is a strong Lewis acid in a combination with a smallconcentration of a Broensted acid, is a preferred catalyst component inthe ionic liquid catalyst scheme.

While not being bound to this or any other theory of operation, thepresent invention is based in part on our discovery that one of themajor catalyst deactivation mechanisms is the formation of by-productsknown as conjunct polymers. The term conjunct polymer was first used byPines and Ipatieff to distinguish these polymeric molecules from theusual polymers. Unlike typical polymers, conjunct polymers arepolyunsaturated cyclic, polycyclic and acyclic molecules formed byconcurrent acid-catalyzed reactions including, among others,polymerization, alkylation, cyclization, and hydride transfer reactions.Conjunct polymers consist of unsaturated intricate network of moleculesthat may include one or a combination of 4-, 5-, 6- and 7-membered ringsin their skeletons. Some examples of the likely polymeric species werereported by Miron et al. (Journal of chemical and Engineering Data,1963) and Pines (Chem. Tech, 1982).These molecules contain double andconjugated double bonds in intricate structures containing a combinationof cyclic and acyclic skeletons.

The conjunct polymers deactivate the chloroaluminate ionic liquidcatalysts by weakening the acid strength of the catalyst through theformation of complexes of conjunct polymers and AlCl₃ possibly by meansof electron-donor/electron-acceptor interactions. The conjunct polymerswith their double bonds are the donors and the Lewis acid (AlC₃) is theacceptor. Using their double bonds, the conjunct polymers coordinate tothe Lewis acid (AlCl₃) in the ionic liquid and rendering thebutylpyridinium chloroaluminate catalyst less active. Thus, the acidityof the catalyst becomes weaker and the overall catalytic activitybecomes compromised and no longer effective for the intended purpose.Thus, the catalyst performance will become a function of theconcentration of conjunct polymers in the ionic liquid phase. As moreconjunct polymers accumulate in the ionic liquid phase the catalystbecomes less active. So, removal of all or a suitable portion of theconjunct polymers from the ionic liquid phase is a significant aspect ofthe present process for ionic liquids catalyst regeneration.

The term “conjunct polymer” as used herein also includes any otherspecies which might complex to AlCl₃ by pi bonding or sigma bonding orother means, which results in those species binding to the ionic liquid,so they are not removable by simple hydrocarbon extraction.

It is believed that deactivation of the catalyst by the presence ofconjunct polymers is, in part at least, caused by coordination andcomplex formation between the Lewis acid AlCl₃ (electron pair acceptor)and the conjunct polymers (electron donors). In such complexes, theAlCl₃ is no longer available for catalysis since it is tied-up in theAlCl₃-conjunct polymers complexes. It also appears that the presence (oraccumulation) of conjunct polymer molecules in the catalyst phase is notby virtue of being miscible in the ionic liquid phase. While conjunctpolymers may be somewhat miscible in the ionic liquids, theiraccumulation in the catalyst phase is more likely to being bound bystrong acid-base interactions (complexation) rather than being solublein the ionic liquid phase.

Conjunct polymers isolated from the catalyst phase by means ofhydrolysis are highly soluble in hydrocarbons. However, attempts toremove them from the catalyst phase prior to hydrolysis by simpleextraction methods with hydrocarbon solvents such as hexane, decane andtoluene were unsuccessful. Other more polar solvents such as CH₂Cl₂ maydissolve a chloroaluminate ionic liquid and therefore are not selectivesolvents for dissolving and removing conjunct polymers. Conjunctpolymers may be isolated by hydrolysis. However, these methods ofisolating the conjunct polymers are destructive, and result in an actualloss of a catalytic component (AlCl₃). The hydrolysis methods hydrolyzethe catalytic component (AlCl₃) and transform it into inactive aluminumhydroxide and aluminum oxide. This indicates that the conjunct polymersare tightly held in the ionic liquid phase by fairly strong type ofbonding system. Therefore, any successful attempt to reactivate andregenerate the catalyst must involve the removal of conjunct polymers torelease aluminum trichloride from the AlCl₃-conjunct polymer complexeswithout destroying, consuming, or irreversibly tying up the AlCl₃. Inother words, one objective is to free the catalyst by replacing theconjunct polymers with other basic species that simply displace thepolymer without destroying the catalyst or by suppressing the ability ofconjunct polymers to form complexes with Lewis acids (aluminumchloride).

The deactivated catalyst can be revived in a nondestructive manner byfreeing up the AlCl₃ from conjunct polymer-AlCl₃ complex. In principle,this can be accomplished by saturation of the double bonds of theconjunct polymers to eliminate their ability to coordinate to the Lewisacid (AlCl₃). By hydrogenation, the double bonds of the conjunctpolymers will be saturated and no longer be able to be coordinated orcomplexed to AlCl₃. AlCl₃ no longer bound by conjunct polymers is thenreleased to take part in catalytic reactions.

Among other things the present invention provides a process for theremoval of the conjunct polymers from a used ionic liquid catalyst bysaturating the double bonds of the conjunct polymers by means ofhydrogenation using a metal or metal alloy hydrogenation catalyst.

Hydrogenation is a well-established process both in the chemical andpetroleum refining industries. Nickel is often used as a hydrogenationcomponent, as are noble metals such as platinum, palladium, rhodium andiridium. Depending upon the ease with which the feed may behydrogenated, the hydrogen pressures used may vary from quite low tovery high values, typically from about 100 to 2,500 psig.

The hydrogenation catalyst used in this invention may be any one of thevarious metallic catalysts which have hydrogenating ability. Thepreferred catalyst is selected from Group VI-B and VIII. Specificexamples of the metallic catalysts are Fe, Co, Ni, Ru, Rh, Pd, Ir, Os,Pt, Cr, Mn, Ti, V, Zr, Mo, and W. These metals may be used singly, incombination or as alloys. Catalysts such as Raney nickel and alloys suchas Ni/Al alloy may also be suitably employed.

The metals can be in the form of fine particles, granules, sponges,gauzes, etc. Each metal may be used in any number of forms: (1)macroscopic, which includes wires, foils, fine particles, sponges,gauzes, granules, etc.; and (2) microscopic, which includes powders,smokes, colloidal suspensions, and condensed metal films.

It is known that Raney-type-metal catalysts are prepared from alloyscontaining one or more catalytically 25 active metals (e.g., Ni, Co, Fe,Cu, Pd, etc.) and one or more catalytically inactive, easily dissolvablemetals (e.g., Al, Si, Mg, Zn). The catalytically active metal componentof the alloy is present in a so-called “dissolved” state, i.e. in afinely divided form. The inactive component is removed from the alloy byleaching the same with a solvent which does not attack the active metal.As solvents, generally aqueous alkaline solutions are used. During thisprocedure the active metal remains in the form of finely dividedcatalyst. The activity of the thus-obtained catalysts is higher thanthat of catalysts prepared, e.g., by reducing the appropriate metaloxides. This high activity explains the importance and the widespreaduse of such catalysts.

As noted previously, ionic liquid catalysts may become deactivatedduring use. For example, in an alkylate production unit, light (C₂-C₅)olefins and isoparaffin feeds are contacted in the presence of acatalyst that promotes the alkylation reaction. In one embodiment of aprocess in accordance with the present invention, this catalyst is achloroaluminate ionic liquid. The reactor, which may be a stirred tankor other type of contactor (e.g., riser reactor), produces a biphasicmixture of alkylate hydrocarbons, unreacted isoparaffins, and ionicliquid catalyst containing some conjunct polymers. The densecatalyst/conjunct polymer phase may be separated from the hydrocarbonsby gravity settling in a decanter. This catalyst will be partiallydeactivated by the conjunct polymers binding to AlCl₃. The recoveredcatalyst can be reactivated in a reaction system hydrogenation with ahydrogenation catalyst. The products of this step will be reactivatedcatalyst and hydrogenated conjunct polymers among others as describedherein. The reactivated catalyst and the hydrogenated conjunct polymerscan be separated, for example, by solvent washing, decantation, andfiltration.

In one embodiment of the present invention with reference to the FIGURE,a used ionic liquid catalyst/conjunct polymer mixture is introducedcontinuously into a regeneration reactor, which contains a hydrogenationcatalyst.

Hydrogen gas and inert hydrocarbons in which hydrogenated conjunctpolymers are soluble are fed into the reactor at the desired rate. Theinert hydrocarbons may be a normal hydrocarbons ranging from C₅-C₁₅ andtheir mixtures, preferably C₅-C₈ although other hydrocarbons may beemployed. The residence time, temperature and pressure of the reactorwill be selected to allow adequate hydrogenation of the conjunctpolymers. The reaction product is withdrawn and sent to a separator.This mixture is then separated into three streams, one comprisinghydrogen and light hydrocarbons, a second comprising inert hydrocarbonsand saturated conjunct polymers and a third comprising regenerated ionicliquid catalyst. A gravity decanter is used to separate the mixture,from which the ionic liquid phase, which is denser than other componentsis withdrawn. The reactivated ionic liquid catalyst is returned to thealkylation reactor. The solvent/conjunct polymer mix is separated bydistillation to recover the solvent.

It is not necessary to regenerate the entire charge of catalyst. In someinstances only a portion or slipstream of the catalyst charge isregenerated. In those instances only as much ionic liquid catalyst isregenerated as is necessary to maintain a desired level of catalystactivity in the process in which the ionic liquid is used as thecatalyst.

The block diagram in the FIGURE is not meant to restrict the presentinvention any sort or type of reactor. Also, the FIGURE shows an inerthydrocarbon entering the reactor together with hydrogen and thedeactivated ionic liquid. That is an optional implementation. Thehydrocarbon could be left out entirely or it could be added to theseparator to allow extraction and separation simultaneously. Othermodifications are possible and are included in the scope of the presentinvention.

Hydrogenation conditions will generally include temperatures of −20°C.−200° C., preferably 50°-10° C. pressures of atmospheric-5000 psig,preferably 50-500 psig, and a contact time of 0.1 minute-24 hours, andpreferably from ½-2 hours in a normal hydrocarbon as a solvent.

The following Examples are illustrative of the present invention, butare not intended to limit the invention in any way beyond what iscontained in the claims which follow.

EXAMPLES Example 1 Preparation of Fresh 1-ButylpyridiniumChloroaluminate Ionic Liquid Catalyst A (Fresh IL A)

1-butyl-pyridinium chloroaluminate is a room temperature ionic liquidprepared by mixing neat 1-butyl-pyridinium chloride (a solid) with neatsolid aluminum trichloride in an inert atmosphere. The syntheses ofbutylpyridinium chloride and the corresponding 1-butyl-pyridiniumchloroaluminate are described below. In a 2-L Teflon-lined autoclave,400 gm (5.05 mol.) anhydrous pyridine (99.9% pure purchased fromAldrich) were mixed with 650 gm (7 mol.) 1-chlorobutane (99.5% purepurchased from Aldrich). The neat mixture was sealed and let to stir at125° C. under autogenic pressure over night. After cooling off theautoclave and venting it, the reaction mix was diluted and dissolved inchloroform and transferred to a three liter round bottom flask.Concentration of the reaction mixture at reduced pressure on a rotaryevaporator (in a hot water bath) to remove excess chloride, un-reactedpyridine and the chloroform solvent gave a tan solid product.Purification of the product was done by dissolving the obtained solidsin hot acetone and precipitating the pure product through cooling andaddition of diethyl ether. Filtering and drying under vacuum and heat ona rotary evaporator gave 750 gm (88% yields) of the desired product asan off-white shiny solid. ¹H-NMR and ¹³C-NMR were consistent with thedesired 1-butyl-pyridinium chloride and no impurities were observed.

1-butylpyridinium chloroaluminate was prepared by slowly mixing dried1-butylpyridinium chloride and anhydrous aluminum chloride (AlCl₃)according to the following procedure. The 1-butylpyridinium chloride(prepared as described above) was dried under vacuum at 80° C. for 48hours to get rid of residual water (1-butylpyridinium chloride ishydroscopic and readily absorbs water from exposure to air). Fivehundred grams (2.91 mol.) of the dried 1-butylpyridinium chloride weretransferred to a 2-Liter beaker in a nitrogen atmosphere in a glove box.Then, 777.4 gm (5.83 mol.) of anhydrous powdered AlCl₃ (99.99% fromAldrich) were added in small portions (while stirring) to control thetemperature of the highly exothermic reaction. Once all the AlCl₃ wasadded, the resulting amber-looking liquid was left to gently stirovernight in the glove box. The liquid was then filtered to remove anyun-dissolved AlCl₃. The resulting acidic 1-butyl-pyridiniumchloroaluminate was used as the catalyst for the alkylation ofisopentane with ethylene.

Example 2 Preparation of “Deactivated” 1-Butylpyridinium ChloroaluminateIonic Liquid Catalyst (Deactivated Catalyst A)

“Deactivated” or “used” 1-butylpyridinium chloroaluminate ionic liquidcatalyst was prepared from “fresh” 1-butylpyridinium chloroaluminateionic liquid catalyst by carrying out the isobutane alkylation reactionin a continuous flow microunit under catalyst recycle with acceleratedfouling conditions.

The microunit consists of feed pumps for isobutane and butenes, astirred autoclave reactor, a back pressure regulator, a three phaseseparator, and a third pump to recycle the separated ionic liquidcatalyst back to the reactor. The reactor was operated at 80 to 100 psigpressure and with cooling to maintain a reaction temperature of ˜10° C.To start the reaction, isobutane, butenes, and HCl were pumped into theautoclave at the desired molar ratio (isobutane/butenes>1.0), throughthe back pressure regulator, and into the three phase separator. At thesame time, fresh chloroaluminate ionic liquid catalyst was pumped intothe reactor at a rate pre-calculated to give the desired catalyst/feedratio on a volumetric basis. As the reaction proceeded, ionic liquidseparated from the reactor effluent and collected in the bottom of thethree phase separator. When a sufficient level of catalyst built up inthe bottom of the separator, the flow of fresh ionic liquid was stoppedand catalyst recycle from the bottom of the separator was started. Inthis way, the initial catalyst charge was continually used and recycledin the process.

The following process conditions were used to generate DeactivatedCatalyst A (1-butylpyridinium chloroaluminate ionic liquid catalyst)from Fresh Catalyst A: Process Variable Isobutane pump rate 4.6 g/minButene pump rate 2.2 g/min IL Catalyst pump rate 1.6 g/min HCl flow rate3.0 SCCM pressure 100 psig temperature 10 ° C.

The reaction was continued for 72 hours when it was judged that thecatalyst had become sufficiently deactivated.

Example 3 Determination of the Amounts of Conjunct Polymer and OlefinOligomers in Deactivated IL A

The wt % of conjunct polymers in the spent (deactivated) ionic liquidwas determined by hydrolysis of known weights of the spent catalyst. Theexample below is a typical procedure for measuring conjunct polymers ina given spent catalyst. In a glove box, 15 gm of a spent ionic liquidcatalyst in a flask were rinsed first with 30-50 ml of anhydrous hexaneto remove (from the spent catalyst) any residual hydrocarbon or olefinicoligomers. The hexane rinse was concentrated under reduced pressure togive only 0.02 gm of yellow oil (0.13%). Then, 50 ml of anhydrous hexanewas added to the rinsed catalyst followed by slow addition of 15 ml ofwater, and the mixture was stirred at 0° C. for 15-20 minutes. Theresulting mixture was diluted with additional 30 ml hexanes and stirredwell for additional 5-10 minutes. The mixture was allowed to settle downto two layers solution and some solid residue. The organic layer wasrecovered by decanting. The aqueous layer was further washed withadditional 50 ml hexanes. The hexanes layers were combined and driedover anhydrous MgSO₄, filtered and concentrated to give 2.5 gm (16.7 wt% of the spent catalyst) of viscous dark orange-reddish oil. It wasdetermined therefore that this particular spent catalyst contains 0.13%oligomers and 16.7% conjunct polymers. The hydrolysis can also beaccomplished using acidic (aqueous HCl) or basic (aqueous NaOH)solutions.

Example 4 Characterization of Recovered Conjunct Polymer fromDeactivated IL A

The recovered conjunct polymers according to the procedure described inExample 3 were characterized by elemental analysis and by infrared, NMR,GC-Mass and UV and spectroscopy methods. The recovered conjunct polymershave hydrogen/carbon ratio of 1.76 and chlorine content of 0.8%. ¹H-NMRand ¹³C-NMR showed the presence of olefinic protons and olefiniccarbons. Infra Red indicated the presence of olefinic regions and thepresence of cyclic systems and substituted double bonds. GCMS showed theconjunct polymers to have molecular weights ranging from 150-mid 600s.The recovered conjunct polymers have boiling ranges of 350-1100° F. asindicated by high boiling simulated distillation analysis. UVspectroscopy showed a UV λ_(max) at 250 nm pointing highly conjugateddouble bonds systems.

Example 5 Removal of Conjunct Polymer from Deactivated Catalyst A byHydrogenation over Ni—Al Alloy

As a way for regenerating deactivated chloroaluminate ionic liquids, 35gm of spent ionic liquids containing 22.3 wt % (7.8 gm) conjunctpolymers in a 300 cc autoclave, 2 gm of Ni—Al alloy and 70 ml ofanhydrous hexane were added. The autoclave was sealed and pressurizedwith hydrogen to 500 psi and heated to 100° C. while stirring at >1200rpm for ˜1.5 hrs. The starting pressure was 500 psig at roomtemperature. As the autoclave heated up, the pressure rose to 620 psig.As the reaction continued, pressure dropped to 560 psig and remained atthat pressure for the remainder of the reaction time. The reactor wascooled down and to the contents allowed to settle. The resultantreaction mixture contained the hexane layer (the top layer), the ionicliquid layer (the bottom layer) and the Ni—Al alloy settled to thebottom of the reactor. The hexane layer was decanted off and saved. Theionic liquid layer was rinsed 3×50 ml anhydrous hexane. The hexane fromthe reaction and all hexane rinses were combined and dried over MgSO4.Filtration and concentration of the hexane under reduced pressure (˜24torr) in a hot water bath (˜75° C.) gave 6.9 gm of slightly faint yellowoil (88.5% of the expected saturated conjunct polymers). The totalconjunct polymers removed by hydrogenation over Ni—Al at 100° C. and 500psi H₂ pressure was 94%.

Example 6

Example 5 above was repeated with 50 gm of spent ionic liquid containing24.3 wt % (12.15 gm) conjunct polymers in 70 cc hexane in the presenceof 3 gm of Ni—Al alloy at 100° C. and starting hydrogen pressure of 500psi. The reaction ran for 1.5 hrs. A total of 11.5 gm (94.6%) conjunctpolymers were removed from the spent catalyst based on obtainedsaturated polymers and recovered CPs from the hydrolysis of 10 gmportion of the treated ionic liquid catalyst. The remainder of thetreated ionic liquid catalyst was saved and tested for activity asdescribed in example 12.

Example 7 Washing and Reusing Once used Ni—Al Alloy Catalyst forHydrogenation of Conjunct Polymers in Spent Chloroaluminate Ionic LiquidCatalyst

The Ni—Al alloy catalyst that was used to hydrogenate conjunct polymersin the spent catalyst as described in Example 5 above was recovered byfiltration. This recovered catalyst was rinsed with anhydrous methylenechloride (CH₂Cl₂) in frit glass funnel under house vacuum in glove box.The rinsed Ni—Al catalyst was dried under house vacuum and used again asin Example 5. The results showed the same degree of removal of conjunctpolymers as in Example 5.

Example 8 Hydrogenation of Conjunct Polymers in Spent ChloroaluminateIonic Liquid Catalyst over Nickel Metal

As in Example 5 above, 25 gm of spent chloroaluminate ionic liquidcatalyst containing 15.5 wt % (3.87 gm) conjunct polymers in 60 mlanhydrous hexane (in 300 cc autoclave) was hydrogenated at 100° C. and500 psi hydrogen pressure over Nickel metal (3 gm) for 1.5 hours. Oncethe heating started, the pressure steadily started rising until itreached 946 psi at 100° C. The pressure dropped slightly to 910 psi atthe end of the run. The reaction was stopped and the organic phasecontaining the hydrogenated polymers was decanted off. The ionicliquid-Ni residue was rinsed with 2×50 ml anhydrous hexane. All theorganic layers were combined and dried over MgSO4. Filtration andconcentration to remove hexane gave 1.58 gm (41 %) of the hydrogenatedpolymers as colorless oil. The ionic liquid catalyst was separated fromNickel metal by filtration. The ionic liquid catalyst was entirelyhydrolyzed giving 1.62 gm conjunct polymers (the total amount of CPsremaining in the catalyst). This indicates that hydrogenation overNickel metal led to the overall removal of 2.2 gm (58%) of the conjunctpolymers from the spent catalyst.

Example 9 Removal of Conjunct Polymer from Deactivated Catalyst byHydrogenation with Nickel Boride Catalyst

The procedure of Example 5 was repeated using 22.00 gram of spentchloroaluminate ionic liquid containing 7.75 wt % conjunct polymer. Thehydrogenation catalyst was 1.0 gram of nickel boride catalyst. In thisexperiment, no hexane was added to aid stirring. The initial pressure at100° C. was ˜1312 psig and after heating 4.5 hours at 100° C., thepressure was ˜1300 psig. After extraction of hexane and evaporation oflight components, no oil was recovered.

The entire sample of the deactivated Chloroaluminate ionic liquid afterhydrogenation and hexane extraction was placed in a bottle andhydrolyzed as described in Example 3. After hexane extraction andevaporation of the volatiles from the combined hexane extracts, aresidue of 0.97 g of conjunct polymer was obtained. This corresponds toa conjunct polymer content after hydrogenation of 4.41 wt %.Alternatively, 43.1 wt % of the conjunct polymer originally present inDeactivated Catalyst A was removed by hydrogenation.

Example 10 Determination of the Activity of the RegeneratedButylPyridinium Chloroaluminate Ionic Liquid Catalyst by Hydrogenationover Ni—Al Alloy

The regenerated butylpyridinium chloroaluminate ionic liquid catalystdescribed in Examples 5 and 6 was tested for activity by using it as thecatalyst in the alkylation of isopentane with ethylene and comparing itwith freshly-made catalyst. The alkylation of isopentane with ethylenewas done according to the following procedure A 300 cc autoclave wascharged with 20 gm of ionic liquid catalyst, 100 gm anhydrousisopentane, 10 gm ethylene and 0.3 gm anhydrous HCl. The reaction wasthen stirred ˜1200 rpm and heated to 50° C. at autogenic pressures. Thestarting pressure was usually 280-320 psi. The reaction was usuallycomplete when the pressure dropped down to single digits. In the case ofslow going reaction, the reaction was allowed to go on for 1 hr. At theend of the reaction, the reactor was vented out and a gas sample waschecked by GC for ethylene concentration. The liquid reaction mixturewas allowed to settle into 2 phases. The organic phase was decanted andanalyzed for product distribution by GC analysis. The following Table 1draws a comparison among the freshly made, the spent and the regeneratedcatalysts. TABLE 1 Fresh Ionic Spent Ionic Ni—Al Regen. Liquid CatalystLiquid Catalyst Ionic Liquid Cat. Reaction Time 6-9 min. 60 min. 4-7min. Starting 300 psi 286 psi 350 psi Pressure Ending pressure 11 302psi 7 iC5 wt % 72 98 61 C7s wt %: 2,3-DM-Pentane 8.23 0.9 8.52,4-DM-Pentane 10 0.6 11.3 Other C7s 0.77 0.1 1.2 2,3DM/2,4DM 0.82 1.50.75

1. A process for regenerating a used acidic ionic liquid catalystcomprising contacting the used ionic liquid catalyst and hydrogen with ametal hydrogenation catalyst in a reaction zone under hydrogenationconditions for a time sufficient to increase the activity of the ionicliquid catalyst.
 2. A process according to claim 1, wherein thehydrogenation catalyst is selected from the group consisting of GroupVI-B and VIII elements, their alloys and their mixtures.
 3. A processaccording to claim 1, wherein the catalyst is a Raney metal catalyst. 4.A process according to claim 1, wherein the hydrogenation catalyst is ina microscopic form.
 5. A process according to claim 1, wherein thehydrogenation catalyst is in a macroscopic form.
 6. A process accordingto claim 1, wherein the reaction zone contains an inert hydrocarbon inwhich saturated conjunct polymers are soluble.
 7. A process according toclaim 5, wherein the inert hydrocarbon is selected from the groupconsisting of normal hydrocarbons ranging from C₅-C₁₅ and theirmixtures.
 8. A process according to claim 1, wherein the ionic liquidcatalyst has been used to catalyze a Friedel-Craft reaction.
 9. Aprocess according to claim 8, wherein the Friedel-Craft reaction isalkylation.
 10. A process according to claim 1, wherein the ionic liquidcatalyst comprises an imidazolium, pyridinium, phosphonium ortetralkylammonium derivative or their mixtures.
 11. A process accordingto claim 1, wherein the ionic liquid catalyst is a chloroaluminate ionicliquid.
 12. A process according to claim 11, wherein the ionic liquidcatalyst is a chloroaluminate ionic liquid.
 13. An ionic liquidcatalyst, which has been regenerated in accordance with the process ofclaim
 1. 14. A process for regenerating a used acidic ionic liquidcatalyst which has been deactivated by conjunct polymers comprising thesteps of contacting the used ionic liquid catalyst and hydrogen with ametal hydrogenation catalyst in a reaction zone under hydrogenationconditions in the presence of an inert hydrocarbon in which saturatedconjunct polymers are soluble for a time sufficient to hydrogenate atleast a portion of the conjunct polymers.
 15. A process according toclaim 14, wherein the inert hydrocarbon is selected from the groupconsisting of normal hydrocarbons ranging from C₅-C₁₅ and theirmixtures.
 16. A process according to claim 14, wherein the hydrogenationcatalyst is selected from the group consisting of Group VI-B and VIIIelements, their alloys and their mixtures,.
 17. A process according toclaim 14, wherein the catalyst is a Raney metal catalyst
 18. A processaccording to claim 14, wherein the hydrogenation catalyst is in amicroscopic form.
 19. A process according to claim 14, wherein thehydrogenation catalyst is in a macroscopic form.
 20. A process accordingto claim 14, wherein the ionic liquid catalyst has been used to catalyzea Friedel-Craft reaction.
 21. A process according to claim 14, whereinthe Friedel-Craft reaction is alkylation.
 22. A process according toclaim 14, wherein the ionic liquid catalyst comprises an imidazolium,pyridinium, phosphonium or tetralkylammonium derivative or theirmixtures.
 23. A process according to claim 14, wherein the ionic liquidcatalyst is a chloroaluminate ionic liquid.
 24. A process according toclaim 22, wherein the ionic liquid catalyst is a chloroaluminate ionicliquid.
 25. An ionic liquid catalyst, which has been regenerated inaccordance with the process of claim 14.